While the most widely used method of sterilization in hospitals is steam sterilization, this method is not always practical, because of adverse effects on materials to be sterilized. The long turn around time required for ethylene oxide sterilization often makes this alternative method not practical. A rapid, low temperature method for disinfecting and sterilizing surgical items relies on the use of an alkaline glutaraldehyde solution ("AGS") as the disinfectant/sterilant. The solution is generally used at a 2% concentration.
Studies indicate that the pH of the AGS solution affects both its stability and its biocidal activity. At an acid pH of about 3-4, glutaraldehyde solutions are stable for a period of about two years. However, at low pH levels, AGS does not exhibit exceptional sporicidal activity. The alkalinization of AGS on the other hand, while it optimizes antimicrobial activity, as well as sporicidal activity, promotes an aldehyde polymerization reaction which results in a gradual loss of antimicrobial activity of the AGS.
AGS is considered biocidally active above one percent aldehyde concentration. As a result of alkalination an AGS solution having an initial glutaraldehyde concentration of 2.1% at a pH of 8.5 will degrade over a period of about 28 days at ambient temperatures to a concentration of about 1.3% glutaraldehyde with a concommitant decrease in pH to about 7.4. This chemical degradation limits the useful life of buffered glutaraldehyde to 14 to 28 days depending on the nature and concentration of the buffering agent.
Commercially, AGS is usually supplied at a glutaraldehyde concentration of 2%. To insure effectiveness suppliers advise customers of the effective life of the product, after which time it is recommended that the AGS be discarded. Illustrative of these commercial products and their recommended useful lives are the 2% GA shown in Table I.
TABLE I ______________________________________ Product 2% Glutaraldehyde Recommended (Trademark) pH Useful Life (Days) ______________________________________ CIDEX 7.8 14 CIDEX 7 7.9 28 Glutarex 7.6 28 *Wavicide 6.2 28 ______________________________________ *unbuffered
Since excessive organic loads (blood, pus, mucus, etc.) reduce the effectiveness of AGS, and reuse results in dilution of the solution as a result of rinse water brought in with instruments and AGS removed upon removal of the instruments, time alone is not necessarily determinative of the degree of degradation of an AGS. The effect of these factors on AGS use life cannot be directly expressed quantitatively since the pertinent parameters are not readily measurable. Consequently, in order to insure that the AGS is effective, hospital staff may discard AGS well before the end of the recommended use life. It is known, however, that to obtain kill in all samples of micro-organisms and viruses the lowest concentration of glutaraldehyde which is effective is 1%.
All of the official methods for determining the effectiveness of disinfectants which have been established by the Association of Official Analytical Chemists are complex, time consuming and beyond the technical capabilities of and time constraints on the nusing staffs which use AGS. A new effectiveness test for a particular brand of AGS, Cidex 7, was introduced into commercial distribution recently by Surgikos, Inc. The test method involves the use of a "kit" with a seven step procedure which includes the exact measurement of two reagents, the careful measurement of two others, and a color comparison for determining concentration. A blue color is obtained when the glutaraldehyde concentration falls to 1% or below, and is to be interpreted as the time to replace the AGS. While this test is effective, the industry has long sought a simple "go-no go" test which can be carried out quickly without any need for special care or skill by the operator. Heretofore, no such test has been available.